I'm making a Drupal 7 site that has an event content type. There are two user roles: venues and speakers, and both can create events. I need a way for both to be referenced in the node (with auto-complete), but keeping in mind that they won't necessarily have an account on my site.
Example 1: The venue "Big Conference Center" creates a new event called "Cool Conference 2012". Their speaker is John Doe, so they enter his name in a text box, it finds him using user role Speaker auto-complete, and he is referenced. If you go to John's user page now, it lists Cool Conference 2012 as an event he is speaking at.
Example 2: The same venue creates another event. This time the speaker is Jane Anon, who doesn't have an account on the site. The auto-complete returned nothing, so Jane Anon is stored in plain text in that field. When Jane Anon joins the site two weeks later, she is presented with a list of events that match her name, and she can select which ones are hers. Then, the plain text changes to a reference.
Examples 1 and 2 should work the same if it's the speaker who is creating the events and the venue who is referenced.